When you're just getting started, you only really need one or two sections. But as your store grows, it's important to organize your store into sections that make logical sense. For one thing, it makes it easier for potential customers to browse. Secondly, when a potential customer clicks on one of your listings, ETSY will scroll other products in that section over to the right- so it serves as cross promotion.
When you click on the sections tab, you can re-organize you store by moving existing listings into new store sections.
